The dual nature of hypothalamic-pituitary-adrenal axis regulation in dyads of very preterm infants and their mothers.

•Mother-infant HPA axis co-regulation is key to infants’ socio-emotional development.•We compared HPA axis co-regulation in dyads of VPT and full-term (FT) infants.•HPA axis co-regulation was observed across a socio-emotional stress-inducing task.•VPT dyads appear to be less able to dynamically coordinate HPA axis regulation.•Both methodological and clinical implications of these findings are discussed.